Abstract The biogeochemical cycling of trace metals (TMs) in coastal embayments is strongly modified by human activities, yet process‐based understanding is often limited by a lack of phase‐resolved observations. We investigated the distributions, sources and partitioning of seven TMs (Mn, Fe, Ni, Cu, Zn, Cd, Pb) among dissolved, labile particulate and refractory particulate pools during spring in Daya Bay, an industrialized bay in the South China Sea. Phase‐resolved observations and comparison with adjacent shelf and offshore regions show marked elevation: surface dissolved metals are typically 1.4–38 times higher than in surrounding South China Sea waters, primarily driven by anthropogenic inputs (industrial/urban effluents) and metal‐rich freshwater (rivers and groundwater), and mean particulate Mn, Ni and Cu exceed Pearl River–influenced levels by up to one order of magnitude. Particulate Mn, Fe, Zn, and Pb are primarily controlled by lithogenic inputs, sediment resuspension, and particle scavenging, with Mn exhibiting a large non‐sedimentary labile component consistent with widespread formation of Mn‐oxide. Particulate Cu and Cd exhibit strong biogenic control; thermally enhanced phytoplankton growth near nuclear power plant outfalls further amplifies their elevated particulate concentrations during spring. Ni shows a mixed signature, with a refractory lithogenic background, modest biogenic association and localized increases in the labile particulate fraction near industrialized shorelines. These results demonstrate that resolving dissolved, labile and refractory particulate phases is critical for diagnosing trace‐metal sources and transformations, and provide a transferable framework for assessing ecological risks in rapidly developing coastal seas.
Ge et al. (Mon,) studied this question.